1. Field of the Invention
The present invention relates to eprom emulators, and more particularly pertains to the field of paging eproms and their emulation for the purpose of developing hardware and software in an expeditious manner. The use of paging EPROMs allows the EPROM to act as many individual ROMs because different sets of instructions can accessed by use of a paging circuit. This allows the EPROM to be much more versatile. This also makes the programming more difficult and time consuming. Therefore, there is a need to eliminate this time consuming reprogramming during the development stages of this type of hardware. The present invention allows the programming to be changed virtually instantaneously. This allows the programmers to concentrate on the programming without the worry of having to face a long reburning process for a new test. This in turn leads to a better product since it can be more thoroughly tested before the final EPROM is programmed and any bugs or faults which are found can be eliminated by further testing.
2. Description of the Prior Art
Various types of eprom emulators are known in the prior art. A typical example of such an eprom programmer or emulator is to be found in U.S. Pat. No. 4,578,751, which issued to Edward Erwin on Mar. 25, 1986. This patent discloses the use of a device which is capable of simultaneously programming a large number of EPROMS. U.S. Pat. No. 4,451,903, which issued to Larry Jordan on May 29, 1984 discloses a method of permanently programming an EPROM. U.S. Pat. No. 4,441,167, which issued to Fabio Principi on Apr. 3, 1984, discloses an EPROM which can be programmed by changing the resistance characteristics of the device. U.S. Pat. No. 4,363,109 which issued to Raymond Gardner on Dec. 7, 1982, discloses a method of constructing an EPROM. U.S. Pat. No. 4,319,341, which issued to Toshitaka Fukushima et al on Mar. 9, 1982, discloses a circuit for programming an EPROM.
While the above mentioned devices are suited for their intended usage, none of these devices show the use of static RAM to actively mimic an eprom for the purpose of testing circuitry and software. The prior art devices need to be extensively and time consumingly programmed. The present invention is capable of being programmed quickly by simply throwing a switch and sending the new information to SRAM. This enables reprogramming as often as necessary without the extended programming time needed by traditional EPROM's. This device is especially useful in the field of software development. When placed in the target system with a microprocessor emulation tool, the EPROM emulator can be reprogrammed by simply writing data to its assigned address space. This allows the emulator to be changed as often as necessary and results in a better product. Inasmuch as the art is relatively crowded with respect to these various types of eprom programmers and emulators, it can be appreciated that there is a continuing need for and interest in improvements to such eprom emulators, and in this respect, the present invention addresses this need and interest.